Control circuit for sound recording



Feb- 20, 1945- L THOMPSON Re. 22,606l

u CONTROL CIRCUIT FOR SOUND RECORDING APPARATUSES original Filed Mayra?. 1941 3l l f BY H A J l TTORNEY Rume ret.' 20,1945

CONTROL CIRCUIT FOR SOUND RECORDING APPARATUSES Lincoln Thompson, Cheshire, Conn., `assignor to The Soundscriber Corporation, New Haven, Conn., a corporation of Connecticut A Original No. 2,342,503, dated February 22,

May 27, 1941. Application Serial No. 395,421,

ior reissue December 20, 1944, Serial No. 569,012

comms. ('Cl. 17a-100.4)

This invention relates to phonographs and more particularly to a dictating machine for controlling the recording of sound on thin disk rec`- ords. I

One object of the invention is to provide an apparatus of the above nature employing an A. C motor, and having circuits whereby. said motor may be selectively supplied with A. C. cur-- rent from an A. C. supply line or which may be used with a D. C. supply line by converting the D. C. current through an inverter.

A further object of this invention is to provide means for. short circuiting the' cutting head of the recording apparatus whenthe latter is in recording position and while the operator is not dictating in order to minimize or prevent undesired feed back 'sounds emanating from said cutting head.

A still further object of this invention is to provide a supplementary harness or cord which may be employed for controlling the dictating machine from a remote point, whenever desired.

A still further object is to provide an improved apparatus of the above nature which will be relatively inexpensive to manufacture, simple in construction, compact, ornamental in appear-y ance, and very eicient and durable in use.

With these and other objects in view, which will appear as the description proceeds, there has been illustrated by the accompanying drawing, one form in which the invention may be con- .veniently embodied in practice.

In the drawing: Fi gure 1 is a perspective view. of the sound recorder cabinet of adictating machine togethwitha D. C. inverter box, and anA. C. supply cord apparatus-the units thereof being shown in separated relation.

Figure2 is a diagrammatic view of the circuit ;;Figure.a-isadiagrammatic view showing the circuit:contractionsv of the remote control cord or harnessunmitsgassociatedcontrol switch.

A-The'dic'tatirgg machine oi the present invention is provided itlr.- an electricaly amplifler rwhich may Vopens. either on Arc. pr D. C. curdisk record turntable which rent, but employs-,fa may be drivenvonly by an A. C. motor. Consequently, to operate-fthe dictatingmachine, on D.

C.', it is necessary toA convert the current to'. C.

. for the use yoi vthe motor only. The conversion from D. C. to A. C. is accomplished by a vibrator convertor switch herein designated as an inverter," which is similar to a polarity changer o! the conventional type.

In order to preserve Moreover, by converting only the current Anecessary for the A. C. motor, the inverter will always have thel same load, which results in greater durability and longer life of the contacts and vibrator.

The supplementary remote control is preferably made in the form of a harness or six-wire cord which may be attached to the recorder whenever desired, by merely inserting it within the power circuit. In other words, one end of the harness will be plugged into the dictating machine andthe other end either into the A. C. supply socket or into the D. C. inverter, as the case may be. In this way, the dictators desk will not be littered up with cords, because the branch remote control circuit is the only additional cord located on his desk. This makes for a simple, convenient, and fool-proof system.

Referring now to the drawing, wherein like reference numerals designate like parts throughout the several views, the numeral III indicates the recorder cabinet of a dictating machine of the disk record type, such as was disclosed in my prior patent, No. 2,200,866, issued May 14, 1940, and reissued September 22, 1942, No. Re. 22,183, entitled Apparatus for' recording sound on thin disks." At the rear of the cabinet Ill, provision is made of a 6-prong plug II which is adapted to be detachably connected to a corresponding 6-aperture socket I2 joined to wires I3, I4, I5, I6', and,I1, leading to' an inverter I8, or toa similar socket I9. The socket I9 has six apertures, five of which contain contacts 23, 24, 25, 26, and 21. The two contacts 23 and 26 are connected to a wire 20 leading to one side of a two-prong plug 22 adapted to be inserted into an A. C, power line. The contact 24 is connected to a wire 2I leading to the other side of the two-prong plug 22. Also, the contact 25 is connected with the contact 2l. The sixth aperture has no contact.

The inverter I8 which is used only when D. C.

power is supplied, contains an extension cord 28 ,recorder cabinet III. The switch Si is provided with a pair of switch blades denser 54 and then to I B, at pOintS described.

of the transformer is connected and said coil 8B has three taps I9, I4,

It and I1 which, whenrin closed position. willV engage contacts 3l and 3s from which a pair of conductors 4l and 4| pass to the A. C.D. C. ampliiier 42.

It will thus be seen, that even when the inverter IB is employed, a portion'of the direct current from the supply line will pass directly to the amplifier 42 located within`4 the recording cabinet l0 without being converted to` A. C. cursV rent. I

Thevconductor SII of the inverter is also connected at a point 43 to a conductor 44 leading to a fuse 4l and a choke coil 44, which in turn is connected at a point 41 to a wire 4I. A branch wire 49 leads from a point il on the wire 4l to the wire l1 of the inverter socket ends thereof. The wire is also connected at the point l2 to a conductor l2 leading to a cona wire BI, from which lead three conductors 58, 51, and Il, respectively (see `Figure 2).

The conductor It is connectedthrough an inductance 50 to a wire Il which leads to a crosswire 6| from which depend a pair of contacts 62 and Il. Extending below the wire 4l from the point 52 is a wire I4 lincluding a condenser 65. and said wire which has two connections to the wires l1 and l1 and Il, respectively. The wire Si from a point BI, leads to a wire 1l including on inductance 1| which is connected to a crosswire 12 leading to two contacts 13 and 14 located immediately below and in alinement with the contacts 62, 63. A magnetic reed member 48a, such as iron. lies between the two pairsof contacts 82, 63, and 12, 14, respectively, and has .at its outer extremity a contact 1I which is located adjacent a stationary contact which is connected by a conductor 11 to a point 1l, from which a conductor leads to a nlter circuit con- A taining a resistor l0 and a condenser 8|.-the latter being Joined by a conductor l2 -to the wire 48a at the point B2. The movable reed 48a is also provided with two intermediate contacts 62a and ila, which are adapted to engage the contacts B2, il, and 13. 14, alternately as the reed is vibrated by the solenoid I4 as will be hereafter At the junction point '18, a solenoid I4 is provided, which is connected by a wire II leading to a point intermediate the ends of a transformer primary` coil 81, the latter being con-k nected at its top end to the point Il, and at its bottom end to the point Bl by suitable conductors, as shown in Figure 2. The secondary coil Il to the wire it.

The tap Il is herein shown connected to the wire Il, while the taps 89 and il are idle.

The switch Si always feeds one branch or the supply circuit trrough a two-circuit switch Si t containing two per and lower which move together when tbe switch is opened separate movable converging upor closed. The switch Sz which is of the doublev contact varms "$2, II, respectively,

I2, and said wire I1 includes a condenser 5| intermediate the` sacos conductors lll andV I to the prongs Illl'and lll of the six-prongplug Il and they are adapted to receive the converted A. C. current 'fromithe inverter for driving the motor when the current is supplied from a D. C. power line.

The output from the amplifier 42 is connected to a pair of wires |09 and lill, which lead to a recording head having a needle ||2 for embossing sound grooves upon a record IIJ supported upon a turntable ||4 driven by the A. C. motor |04.

The switch SiA is of the double-pole, singlethrow type and feeds one branch of the supply circuit through the switch Sz which when in upper closed position with the blade 92 engaging the contact 94 feeds the D. C. current back to the inverter unit through the wire 99 and prong |00- thewire I1 serving to energize said inverter unit, and causing it to generate A. C. current which then travels along the wire I5, prong |01, and

, wire |05, respectively. .to the A. C. motor |04, and

B4 leads to a conductor y terminal 21 of the .prong l, and wire I6,

back to the inverter unit through the wire lili,

respectively. A microphone |40 is connected to the input terminals |4| and |42 oi' the amplifier 42.

Operation To operate the machine from a D. C. current supply, when the switch S1 is turned on by means of a hand knob, not shown, (conveniently located on the recorder cabinet HI) the amplifier 42 will ilrst be energized with D. C. The operator will then turn a similar hand knob, not shown, to move the switch Sz from the neutral position shown in Fig. 2 to its upper closed position and energize the inverter Il which in turn will supply the motor |04 with alternating current.

To operate the machine directly from an A. C. supply line, the two wire cords 20 and 2| will be connected to the A. C. line by the plug 22 and the socket I9, and then attached to the sixprong plug I l.

It will be clear that in the socket IIS, the connection of the terminals 23 and 2l together, and the terminals currentr to pass along the prongs 32 and Il lead ing to the terminals 34 and 35 of the switch S1 from which the A. C. current passes through the wire 98 to the upper blade 92 ofthe switch Sz. By meansof this construction, when theswitch Si is thrown into its upper clo'sed position, the current will pass through the contact along the wire 95 to the prong |00 and thence to the socket I9 and thus energize the motor conductors |05 and IIB through the prongs |01 and lill for running the motor from the A. C.

'line. This provides an extremely convenient` arrangement for operating the dictating available, and only using the inverter when the current is supplied by a D. C. power line.

throw type is provided with four contact points 94, 95 Ol, and 81, the contact point being connected by a conductor il to the contact point 39 of the switch Si. The contact i4 is connected by a wire il to one prong lll of the six-prong plug Il. The contact 91 is similarly connected bywire |Il| totbewire |l2leadingtoaprong lofsaidplug The A. C. motor Means to prevent "feed back howling It is a common phenomenon wheremicrophones and loud speakers are employed in close proximity to each other as in public address systems, and electrically amplified dictating magain or amplification bechines,l that when the comes suillciently high and the acoustic coupling between the microphone andthe loud speaker isA sufficiently great, the, objectionable phenomenon as' howling or feedback will be produced. Thus. in a dictating machine, `the rem is connected by a pair or 'u eordlninead mei: wm operate more orvless in s 25 and 21 together permits A. C.y

manner of a loud speaker, and dueto the fact that the microphone is generally located quite close to the recording head, "howling" will fre# quently be produced even without a great amount of amplifier gain.- This howling ii'ect" will be greatly exaggerated if the turntable is stationary, because in this case, not only does the cutting head itself set up sound vibrations in the air but the recording needle which 'is in contact with the disc record will cause said record, as

well as the turntable, to likewiseiun'ction as-a loudspeaker diaphragm. When the turntable is rotating, the disc record will have less diaphragm action, and the cutting head will act much less eilectively as a loud speaker.

According to applicants invention, the above described undesirablev phenomenon has been en- -tlrely avoided by providing means to short circuit the cutting head during "stand by periods when no dictation is taking place, thus doing away with feed back howling, and at the same this, this arrangement permits a much greater amount of ampliiler gain to be used.

This has been accomplished by arranging llicapparatus so that the two-blade switch Sz will perform the function of starting the motor when the switch Sz -is in its upward closed position (with the upper switch blade 92 in contact with the point 94) and of stopping, said motor and short-circuiting thecutting head when said switch S2 is in its lower closed position, at lwhich time the lower switch blade 93 will engage the contact point 81 which isconnected by a wirev |02 to the wire ID3-the upper blade 92 of course being then in open position. 'I'he wire 4| is connected to the wire IIB within the amplifier in order to insure that the cutting head Will be short-circuited when not dictating. l

Remote control apparatusI indicated by the numeral ||5, containing the six individual Wires H6, H1, H8, H9, |20, and I2|.

' each of which is connected at one end to a sixaperture socket |22, and at its other end to a six-prong receptacle |23 having prongs |24, |2'5, |26, |21, |28, and |29, respectively. The receptacle |23 serves to receive the socket I9 from the A. C. power line cord or the socket |2 from the inverter, selectively, according to whether A. C. or D. C. current is being used. In either case, the socket |.22 will be connected to the sixprong plug which is mounted on the recorder cabinet I0.

The receptacle |23 has a branch line control cord consisting of three wires |3|, |32, and |33, leading to a remote control switch |34, which is in series with the motor switch S1 (see Figure 2) of the recorder, and is so constructed that the motor will be started Whenever the movable spring-pressed switch contact member is depressed. Assuming that the motor switch Sn is on, Iwhen the remote control switchis re# leased, a spring |36 will move .the switch member |35 upwardly away from a contact |31 and cause it to engage a contact |38. The common movable contact member |35 of said switch will then short-circuit the cutting head since one side of the cutting head is connected to said member |35 through the wires |32, |20 and other connections as described above.

While there has been disclosed in 'this speciilcation one form in which the invention may invention includes all the modiilcationsand er'ni bodiments coming lowing claims.

Having thus. fully-described the invention, what l is claimed as new 'and for which it is desired to vobtain Letters Patent is:

l.:4 In a phonograph recorder which may operate on A. C. or D. C.. a cutting head having a needle for forming a Asoundgroove on aA record, a motor operable only on.A. C. current `for rotating said record, a microphone, a vacuum tube amplier operable on either A. C. or D. C. for amplifying the sound energy received by said microphone, means to supply to said ampliiler a portion of the current from a D. C. power source, an inverter for converting another portion of said D. C. current to A. C. for operating said driving motor. a switch for connecting said source, to said amplifier, and another switch for connecting said source with said inverter.

2. In a phonograph recorder which may be operated on either'A. C. or D. C., a cutting head Vcurrent for driving said rotating record, a motor operableonly onr AFC. record, a microphone, a vacuum tube amplifier operable on either A. lC. or D. C. for amplifying the electrical energy received from said microphone, means to energize said amplier directly from a source of current, means' to selectively supply A. C. froman A. C. source of power or convert to A. C. the current from a D. C. source and supply said con- -verted A. C. current to said A. C. record-driving motor, a manually-actuated switch for connecting said source to said amplifier and a second manually-actuated switch for connecting said source to said D. C.A. C. converting means. I

3. In a phonograph recorder which maybe operated on either A. C. or D. C., a cutting head having means to produce a sound groove on a rotating record, a motor operable only on A. C. current for continuously driving said record, a microphone, a vacuum tube amplifier operable on either A. C. or D. C. for amplifying the electrical energy received from said microphone, means to. energize said amplifier` directly from a source of current, means .to selectively supply A. C. from an lA. C. source of power or convert to A. C. the curmotor, a branch harness comprising s, three-wire conductor cord leading from said recorder to a point situated remote therefrom, and a.l switch for controlling the turning on and oil of the current supplied to said motor.

4. In a recording apparatus for a dictating machine, an amplifier operable on either A. C. or D. C., means responsive to said amplifier for recording sound vibrations on a. rotating sound record, a microphone connected to the input of said amplier for receiving the dictation to be recorded, a motor operable only on A.-C. for driving said record continuously, means for connection to a source of D. C. for directly supplying D. C. to said amplifier, and inverter means for converting D. C. from said source to A. C. for operating said A. C. motor` and two manually-operated switches for nrst connecting said source directly to said ampliwithin the scopev of the fold a`sourceotD.C.i'ordirectlys1mplyinl D.C.-to said amplitier. and. inverter Y source of D. C. for operating said A. C. motor.

6. Inarecordinsapparatustoradictatingmachine, an amplifier operahie on either A C. or D. C., means responsive to said amplifier for reord.aninverterIoremvstintoA.C..enrrm rromanamdmpinmeamiorutniaina -theconvertedLCmux-raittromsaidinvertertq drive saidA. C.motor,audmeonsnsoeiatedwith saidinverterforby-passinaawiinlldthen. C.

currentfromsaidD.'C.Inruil!liireetlytusaid amplier vithdut conversionto-Lawhereln saidrecordinsapporatmmaybeseleethdyeratedeitheronanaaeurrentlmnborms nacurrentsupply. r

8.1naphonnraphicrecordingamlnhlaa movabkeelectdcairecordinsheadhavlngmeans toprodweasmdfsrooveonamovinlrecorda cording sound vibrations on a rotating record. a

' microphone connected to the input of said ampliiier for receiving the dictation to be recorded. a motor operable only on A. C. for driving said record continuously. means for connection to a source of D. C. for directly 'supplying D. C. to vsaid ampiier. and inverter means for converting D. C.

from said motor.

'1. In a recording apparatus for a dietating machine, a. microphone, a D. C. amplifier connected to said microphone, a continuously rotating record,v an' embossing head responsive to the output of said amplifier for recording sound grooves on said record, an A. C. motor for rotating said recsource to A. C. for operating said A. C.

3o ingheadaiongsaidrecord microphonelocatedincloseproximiwtosaid head.anelectricmotortordrivinsaidrecord,a vacuumtubenmpliiierhavingitsinputemnected withsaidmicrophone andioutputconnected withsaidrecording'mandssinslemanuallyoperatedswitchoperableinonepolitiontosubstantially simultaneously stop said motor and short-circuitsaidrecordingheaiandthusnuliifyanyfeed-backmowlins tendencyduetothe proximityof said micropheme tosaid recording head,saidswitchbeinzoperabiemanotherposi tiontosubstantialiysimuitsneouslyrestoresaid. said motor and recordingheadtotheiroriginal condition, said switch being capable of manual operation at the will of the operator in either direction at any point in the travel of said recordmoLN TnormsoN. 

